Mechanical watches are powered by a mainspring. This spring is the motor of mechanical watches: it is wound up either manually or through the automatic winding-up mechanism when the watch is worn on the wrist and thus stores energy. This is then released continuously to the geartrain.
The geartrain is a kind of gearing mechanism that releases and transmits the high energy from the barrel to the small wheels (minutes wheel, third wheel, seconds' wheel and lever wheel). The escapement as connecting link between geartrain and balance provides for the transmission of the clock pulse and, through the level wheel and the pallets, releases the driving energy from the barrel to the balance and maintains the latter in oscillation. The escapement, controlled by the regulating element, frees and stops the geartrain at very accurate intervals.
The regulating element (controller) comprises a spiral hairspring and a balance wheel (balance). The balance behaves in a way similar to a pendulum, which is always returned to its resting position by means of the spiral hairspring and thus ensures the clock pulse of the watch remains even. In most modern watches, the balance oscillates at 8800 A/h, i.e. eight times per second or nearly 700,000 times per day. These intervals cause the hands to show the “correct time” on the dial.
One disadvantage of mechanical watches by comparison with electronic watches is that the running of a wristwatch is adversely affected by changes in position, fluctuating temperatures, magnetism, dust, irregular winding-up and oils.
EP848842 discloses a timepiece movement whose spring drives through the geartrain a time display and a generator supplying an AC voltage. The generator powers, via a voltage-transformer circuit, a capacitative component and the capacitative component powers an electronic reference circuit with a stable oscillator as well as an electronic control circuit. The electronic control circuit comprises a comparator-logic circuit and an energy dissipation circuit which is connected to an output of the comparator-logic circuit and whose power consumption is controllable through the comparator-logic circuit. An input of the comparator-logic circuit is connected with the electronic reference circuit and another input of the comparator-logic circuit is connected to the generator by means of a comparator step and an anticoincidence circuit. The comparator-logic circuit is designed in such a way that it compares a clock signal coming from the electronic reference circuit with a clock signal originating from the generator, then, in a manner dependent on the result of this comparison, controls the amount of the power consumption of the electronic control circuit by means of the magnitude of the power consumption of the energy dissipation circuit, and in this manner controls the movement of the generator and thus also the operation of the time indicator by controlling the power consumption of the control circuit.
The clockwork from EP848842 requires however a relatively complicated electronics, a generator supplying the energy needed for operating the electronics, as well as a relatively large space for integrating the systems. A further disadvantage of such a timepiece movement is that the forces and torques are different from those of a mechanical clockwork movement, so that the entire clockwork movement needs to be adapted.